It is a century or a centennial
A period of 100 years is called a century.
The year 1013 AD.
It COULD be called a Gigayear, but in practice it is simply called "a billion years".
An anniversaryanniversary: the annual celebration of an event on that day of a previous year
An 150 year celebration is called a Sesquicentennial celebration
An 150 year celebration is called a Sesquicentennial celebration
It is called a "centennial celebration"
A 100 year celebration is called a centennial celebration.
60 year celebration
55th wedding celebration is Emerald.
Centennial
It is called Centenary.
Diamond Jubilee
It is a century or a centennial
An Emerald anniversary
Diamond Jubilee